1. Field of the Invention
The present invention relates to a controller-assisted, manually shifted, synchronized vehicular transmission system including a splitter-type compound transmission. The system will sense a start-from-stop intent to shift the main section, from main section neutral into a start ratio (such as 1st-5th in an 18-speed transmission), and will automatically shift the splitter section into neutral, allowing the synchronized main section to be easily engaged into a target ratio with relatively low synchronizer force and, thus, relatively low driver effort. Upon sensing completion of the main section shift into a main section target start ratio, or upon sensing reengagement of the master clutch, the splitter section will be caused to engage in an appropriate splitter ratio. More particularly, at stop conditions, the splitter is automatically shifted to and retained in neutral only if both the master clutch and the main transmission section are disengaged.
2. Description of the Prior Art
Compound manually shifted mechanical transmissions of the range, splitter and/or combined range/splitter type are in wide use in heavy-duty vehicles and are well known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,754,665; 5,272,929; 5,370,013 and 5,390,561, 5,546,823; 5,609,062 and 5,642,643, the disclosures of which are incorporated herein by reference. Typically, such transmissions include a main section shifted directly or remotely by a manual shift lever and one or more auxiliary sections connected in series therewith. The auxiliary sections most often were shifted by a slave actuator, usually pneumatically, hydraulically, mechanically and/or electrically operated, in response to manual operation of one or more master switches. Shift controls for such systems may be seen by reference to U.S. Pat. Nos. 4,455,883; 4,550,627; 4,899,607; 4,920,815; 4,974,468; 5,000,060; 5,272,931; 5,281,902; 5,222,404; 5,350,561 and 5,737,696, the disclosures of which are incorporated herein by reference.
Three-position splitter actuators and transmission systems utilizing same are disclosed in U.S. Pat. Nos. 5,651,292 and 5,661,998, the disclosures of which are incorporated herein by reference.
Fully or partially automated transmission systems wherein a microprocessor-based electronic control unit (ECU) receives input signals indicative of various system operating conditions and processes same according to logic rules to issue command output signals to one or more system actuators are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,361,060; 4,593,580; 4,595,986; 4,850,236; 5,435,212; 5,582,069; 5,582,558; 5,620,392; 5,651,292; 5,679,096; 5,682,790 and 5,735,771; the disclosures of which are incorporated herein by reference.
Synchronized transmissions and/or transmission sections and synchronized jaw clutch assemblies therefor are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,989,706; 5,738,195 and 5,738,196, the disclosures of which are incorporated herein by reference.
U.S. Pat. No. 4,527,446, the disclosure of which is incorporated herein by reference, discloses a fully automated, blocked-type transmission wherein the main section is automatically shifted to main section neutral during each shift.
Prior art synchronized transmissions for medium- and heavy-duty vehicles were not totally satisfactory, as excessive force was required to operate the synchonizers when engaging a start ratio.